Ok is this correct?

The 69 cars center carb had bowl vent but no vent tube to the valve cover breather.
The 71 cars center carb had bowl vent and the vent tube running to the valve cover breather.
The 70’s I thought just had the vented bowl and no tube like the 69’s but I have seen it both ways?
Was there a date change over or is on just wrong? My 70 auto carb does not have the tube, and a single port breather on the valve cover.